Spitfire Prop

KYsean

Seaman Apprentice
Joined
Jan 7, 2012
Messages
47
Reporting back on the Merc Spitfire prop. I went from a 3 blade Black max 21P to a 4 blade Spitfire 21P (Merc recommends staying with the same pitch for this prop.) Running a 5.0 Mercrusier Alpha 1. With 3 blade, Me, wife two kids and cooler, full fuel I was at 4900 RPM's at WOT 50 mph. This weekend I had the 4 blade Spitfire on the boat. Full fuel, 7 people with cooler and fishing gear for everyone. 4500 RPM at WOT and 45 mph. We skied, tubed and knee boarded all weekend and the boat had no problem at all with all water sports. In fact, pulling a skier out of the water was to easy at times. Had to back off the amount of start throttle. I'm very impressed with this new prop. Our normal load would be 4 people and cooler. Also had the Bimini up all weekend and I'm sure that creates some extra drag.
 
Last edited:

steelespike

Supreme Mariner
Joined
Apr 26, 2002
Messages
19,069
Thats the second impressive Spitfire test I've seen, can't argue with the results.Slip is a little high at 19% but
7 people and gear may account for that.
If we assume 4900 with your normal load and 19% we gets 49.3 mph.If we use 17%(usually slip decreases as rpm goes up) we get 50.5.
Would be interesting to see the actual results.
 

BoatDrinksQ5

Petty Officer 1st Class
Joined
Feb 11, 2012
Messages
377
I look forward to an update on the same for same type test run - more normal loads. At WOT did you find that trim behavior was different at all?

I am in the early stages of my conversion from 3->4blade... :)
 

KYsean

Seaman Apprentice
Joined
Jan 7, 2012
Messages
47
I look forward to an update on the same for same type test run - more normal loads. At WOT did you find that trim behavior was different at all?

I am in the early stages of my conversion from 3->4blade... :)
Trimmed quicker because the new prop gets you on plane much quicker. Sometime in the next week when weather is with us, I'll get it out and report on normal load.
 

KYsean

Seaman Apprentice
Joined
Jan 7, 2012
Messages
47
Update on Spitfire Prop. Had the boat out today with 4 people on board, 3/4 fuel and a cooler of food and water. 3 fishing poles and tackle box. Hit 4850 RPM's at WOT and 48 mph. This would be my normal load on the boat.
 

NEboater28

Cadet
Joined
Apr 30, 2013
Messages
28
I too am interested in the Spitfire Prop. I've had a 2 year saga of props since purchasing my 19 foot Hurricane Sundeck w/ Merc 4.3 IO 220 hp, Alpha Drive. The boat runs heavy at about 4500 lbs with fuel, 3-4 persons on board. I primarily use the boat for skiing, wakeboarding and tubing. I started with a black max 14.5 x 19 (came with boat). Got 50 mph at 4900 RMP (rev limited kicked in with throttle to spare). Then I went to a 4 blade 18 pitch stainless stiletto. The boat was a slug... I used it once and then went to a local prop guy who suggested the merc Alpha 4 aluminum prop. I did this and added trim tabs and my pick up was good but at WOT 4800 (rev limited kicked in), I was down to about 43 mph. In search of the holy grail of props, I got a 19 pitch stainless high-five refurbished. I tried it out recently this last weekend. It seems like the boat was labored with the weight of the stainless prop and my low end 0-12 mph was no different (maybe even slower) than the 4 blade aluminum. This was problematic for skiing as the first 10-15 mph are what gets the skier popped up quick. The high five shined when pulling a tube, after about 2000 rpms, it would pull like a freight train. However, my top end was down to about 40-41 mph and my cruising RPMs went from about 3500 at 30 MPH pulling a skier with the 4 blade alpha to about 4100 RMP at 30 MPH. This equates to burning a lot more fuel and more strain on the engine.

The spitfire appeals to me as the Alpha 4 prop seemed like the best fit for my boat so far, and if the spitfire brings the acceleration and brings back some top end, it might be the prop for me.

Has anyone had the Alpha 4 prop and then switched to a Spitfire? Did you notice a difference... better acceleration and top speed?? Also would I stay with the same pitch as the 19 pitch blackmax that came with the original boat and gave me the best top end?
 

KYsean

Seaman Apprentice
Joined
Jan 7, 2012
Messages
47
I did go from the 3 blade Black max that came with the boat to the Alpha 4. i didn't like it because on a tight turn under power to pick up a downed skier, it would blow out. Went back to the black max until I found the Spitfire. the spitfire will be my main prop now.
 
Top